This invention relates to a magnetron and more particularly to a magnetron provided with an improved microwave output section or antenna.
A microwave oven is generally so designed that any other interior space than a heating chamber having a required volume can be reduced to a minimum to render the microwave oven compact as a whole. Further, it is desired that microwaves be emitted from a magnetron fitted to the microwave oven with a uniform intensity throughout the heating chamber. Therefore, it is customarily demanded that a magnetron used with a microwave oven be substantially compact and the microwave-radiating characteristic of the magnetron be conformable to the design requirements of a microwave oven. However, a conventional magnetron for a microwave oven had its output section formed of a monopole antenna, presenting difficulties in fully meeting the above-mentioned requistes. The monopole antenna linearly extended outward in the axial direction of the cylindrical anode of the magnetron, enlarging the magnetron as a whole by that extent. Where the magnetron oscillated microwaves with a frequency of about 2,450 MHz, the monopole antenna was chosen to have a length of about 3 cm. The magnetron had a hollow cylindrical body 4 cm high and 4.5 cm in diameter. Therefore, the above-mentioned length of the antenna was regarded as unduly large relative to the magnetron body. Microwaves were emitted from the monopole antenna of the magnetron in a direction substantially perpendicular to the axis of the antenna. If, therefore, the magnetron was placed in the upper part of the heating chamber of a microwave oven without any attachment, the aforesaid requirements could scarecely be satisfied. The magnetron had to be fitted to an attachment specially provided for the microwave oven to enable microwaves to be emitted from the monopole antenna with a uniform intensity throughout the microwave oven. However, provision of such attachment properly made the microwave oven large appreciably.